5.6 - Vaccination

• immunity


  ability of an organism to resist infection
• types of immunity


  passive

  active
• acquired immunity


  a resistance to specific pathogens acquired over the lifetime of an organism
• natural immunity


  non-specific immunity you are born with
• passive immunity


  produced by introduction of antibodies into individuals from an external source

  antibodies aren't produced by organism sono memory lymphocytes produced so no lasting immunity
• types of passive immunity

  naturally acquired

  artificially acquired
• naturally acquired passive immunity

  antibodies pass from mother to foetus via placenta or breast milk

  infant doesn't produce any antibodies of its own
• artificially acquired passive immunity

  antibodies in an immune serum are introduced into an organism

  example: anti-venom to treat snake bites
• active immunity


  produced through exposure to antigen which causes the organism to produce its own antibodies
• types of active immunity

  naturally acquired

  artificially acquired
• naturally acquired active immunity

  organism becomes exposed to pathogen naturally & body produces it's own antibodies & memory lymphocytes
• artificially acquired active immunity

  antigens are introduced into organism through vaccines S0 body produces antibodies & memory lymphocytes
• active vs passive immunity

  active immunity requires exposure to antigen & passive immunity doesn't

  passive immunity protection is immediate, active immunity protection takes longer

  in passive immunity memory lymphocytes aren't produced, in active immunity they are

  in active immunity is long term, in passive immunity protection is short term because an tibodies given are broken down
• vaccination


  introduction of a specific antigen by injection or by mouth stimulates immune response
• vaccine


  suspension of harmless antigen introduced into body
• how does vaccine create immunity

  an tigen in vaccine Makes immune system produce antibodies & memory lymphocytes so if antigen enters body again it will quickly the destroyed s0 person doesn't get sick
• Why are booster vaccines given sometimes

  ensure memory lymphocytes are produced
• types of vaccine

  whole-agent vaccines

  subunit vaccines
• antigens in Whole agent vaccines

  whole nonvirulent Microorganisms
• inactivated (killed) antigen in whole agent vaccines

  viruses May be inactivated with formalin or other chemicals

  no risk of infection & there are many antigens
• attenuated (weakened) antigen in whole agent vaccines

  usually strains where mutations have accumulated during culture

  pro: many antigens

  con: not fully inactivated so could replicate
• antigen in subunit vaccines

  contains part or product of Microorganisms that can produce an immune response

  pro: can't replicate

  con: can have fewer antigens
• why are subunit vaccines safer than attenuated vaccines

  they can't replicate in organism

  produce fever adverse effects
• antigenic variation


  arises due to mutations which causes changes to an tigen of pathogen

  Makes treatmen & prevention of disease harder

  harder to develop vaccines
• antigenic variation in influenza virus

  it can recombine its RNA so can change every year so different vaccines must be made

  most effective against the recently circulating strain is administered
• features of a sucessful vaccination program

  vaccine must be economically available in though quantities to immunise most of the vulnerable population

  there must be few side effects

  means of producing, transporting & storing vaccine must be available

  there must be means of administering vaccine properly

  must be possible to vaccinate most of the vulnerable population to produce herd immunity
• how does herd immunity arise

  when enough of the population has been vaccinated to make it hard for pathogen to spread within population

  when most of population is immune it's very unlikely that a susceptible individual will come into contact with an infected individual
• Why is herd immunity important

  it's impossible to vaccinate everyone in a large population

  babies are sometimes too young & it could be dangerous to vaccinate those who are ill
• reasons for vaccines not eliminating disease

  vaccines fail to induce immunity in some people

  individuals may develop disease after vaccination

  antigenic variability

  there may be too many varieties of a pathogen

  some pathogens hide from immune system - inside alls or living in places out of reach

  people may have objections due to religious, ethical or medical reasons
• ethics of vaccines


  development often involves animal testing

  side-effects can cause long-term harm

  must be tested on humans

  to be effective most people must be vaccinated

  in an epidemic who should be vaccinated first
• that's MMR vaccine for

  measles, mumps & rubella
• facts that show there's no link 'between MMR & autism

  author of research was being paid by Legal Aid Board to discover whether parents claimed their children had been damaged by MMR had a case

  study in Japan with 30000 children found no link

  sample size of initial research was very small
• why scientific evidence should be treated with caution

  theory must be critically appraised & confirmed by other Scientists in field

  some scientists may not be acting to tally independently so may be biased

  scientist's personal beliefs, views & opinions may influence how they carry out their research

  facts may be distorted by Media /governments

  new knowledge may challenge beliefs